The present invention relates to a ball bearing, and more particularly to a ball bearing in which balls may be loaded in an annular space formed between the inner ring and the outer ring without use of a cage.
Generally, a ball bearing is to be placed with balls held by the cage between the inner and outer rings. If no cage is used, the balls are adapted to rotate as coming in contact with one another. This may cause damages such as wear or seizure to the balls. However, the cage is not always required for ball bearings to be used for, for example, toy racing cars or casters, which are adapted to be used with a small load or to be rotated at a low speed and to which high precision is not required. For such ball bearings to which high precision is not required, if a high-quality material is used, or cutting or heat treatment is applied, the resultant ball bearings are unnecessarily high in quality to increase the cost thereof.
A ball bearing includes a number of component elements such as sealing elements, etc. For a very small bearing, it is particularly difficult to make such a bearing having a sealing structure.
In a ball bearing, the outer and inner rings are generally made of SUJ2, SUS440C (Japanese Industrial Standard) or the like. After being cut, the rings and other component elements are subjected to heat treatment, abrasion, assembling and the like. Accordingly, the production of a ball bearing takes a lot of manhours.
It is technically difficult to make a ball bearing in which balls are loaded in an annular space between the outer and inner rings without use of a cage.
There is known a method of making such a ball bearing as disclosed by, for example, Japanese Patent Publication No. 50-14236 which corresponds to U.S. Pat. No. 3,657,781. According to this method, balls are loaded between the outer race forming the outer ring and the inner race forming the inner ring, and either the inner or outer races is rotated under application of a pressure by a pair of rollers toward the balls from the outer side of the outer race and the inner side of the inner race, thereby to rolling-form both races.
There is known a ball bearing of which inner and outer rings are respectively made of a forging material and a steel sheet, as disclosed by U.S. Pat. No. 4,603,025 or British Pat. No. 1,007,191. In the ball bearing disclosed by U.S. Pat. No. 4,603,025, the outer ring is made in a U-shape by fitting, to the open side of a L-shape member, a separate lateral plate. Accordingly, the strength is not sufficient. Further, when both lateral plates of the outer ring are brought as close to the balls as possible to decrease the axial distances between both lateral plates and the balls, the width of the outer ring is decreased. This imposes restrictions on the supporting ability of the support member. On the contrary, when the width of the outer ring is increased, the axial distances between both lateral plates of the outer ring and the balls are increased to decrease the rotational performance of the bearing.
In British Pat. No. 1,007,191, the outer ring is made in a U-shape by combining two L-shape members. This presents no problem as to the strength, but the balls are guided by wires disposed at four places, causing the structure to be complicated. Further, since the balls are guided by wire rings, there is the likelihood that the balls are spun so that the ball bearing cannot be used for an application of high-speed rotation if radial and axial loads are exerted. Moreover, since only four rings receive the load exerted to the ball bearing, the ball bearing cannot carry a high load.